Clinical (Cookbook) Neuroanesthesia

Reza Gorji, M.D. Director of Neuroanesthesia University Hospital Syracuse, New York

Neuroanesthesia

• Anesthesia and craniotomy for mass lesions • Anesthesia and craniotomy for aneurysm • Posterior fossa craniotomy • Carotid endarterectomy • GDC • Trigeminal Decompression • Brain Biopsy • Not covered: spine surgery, transphenoidal procedures, awake cranis, closed head injury

Neuroanesthesia

•  Anesthesia for (intracranial) neuroanesthesia requires understanding of relationships between CeBF, CMRO2, and ICP

•  We use techniques and drugs that manipulate these relationships to make surgery and anesthesia successful and safe

•  We do make a difference; when problems occur, the basics are usually violated

Anesthesia and craniotomy for mass lesions

•  Intracranial masses may be congenital, infectious, neoplastic or vascular (ie: clots)

•  Signs of high ICP present( N/V, HTN, bradycardia, personality changes, consciousness level, papilledema, seizures)

•  Growth rate of mass can be guessed from rapidity of symptoms

•  Intracranial compliance curve; effect of slow versus fast volume expansion

Anesthesia and craniotomy for mass lesions Preoperative evaluation

•  Typical history and physical •  Obtain neurological history •  Ascertain presence of high ICP •  SMA7 to look of corticosteroid

induced hyperglycemia, diuretic induce electrolyte abnormalities; anticonvulsant levels

•  CT/MRI for presence of edema, midline shift, location of mass (deep or superficial)

Anesthesia and craniotomy for mass lesions Premedication

•  Premeds include benzodiazepines, corticosteroids, anticonvulsants, diuretics and whatever else is needed to make the patient ready for surgery

•  Watch for signs of hypoxia and hypoventilation

Anesthesia and craniotomy for mass lesions Intraopertative Management

Monitoring

•  ASA monitors •  A-line: Positioning, rapid changes in BP, access for

electrolytes and PaO2 and PaCO2 •  Central Access

•  Where and why? •  When and why?

•  Foley Monitor: Yes •  NMB Monitor: Yes; No MOVEMENT ALLOWED W/

HEAD CLAMPS OR NOT •  Neurologic Monitors as needed: EPs, EEGs, ICP

Monitor* (Zero the ICP monitor at the EAM)

Anesthesia and craniotomy for mass lesions Induction

•  A critical part of the case •  Goals: Minimize raising ICP and

maintaining CeBF •  Technique:

•  Hyperventilate •  Thiopental 1-6 mg/kg •  Fentanyl 3-10 mcg/kg •  Lidocaine 1-2 mg/kg •  Hyperventilate •  NMB •  Intubate efficiently

•  Bad Airway: AWAKE is an option •  Have other drugs ready: esmolol,

NTP, NTG, hydralazine

Anesthesia and craniotomy for mass lesions Positioning

•  Supine Position for frontal/parietal/temporal cranis •  Head is inadvertently turned to one side •  Head Clamp is often placed. AVOID PATIENT

MOVEMENT •  Poor positioning can lead to problems during the

entire case •  Secure your lines before draping •  Put drips close to vein

Anesthesia and craniotomy for mass lesions Maintenance of Anesthesia

•  2 overall techniques: Nitrous-narcotic-relaxant and balance anesthesia with volatile agent

•  Nitrous-narcotic-relaxant technique: 70% nitrous, 30% oxygen, narcotics (fentanyl 2-5 mcg/kg/min), pancuronium 0.02-0.05 mg/kg/hr

•  Balanced: 50-70% nitrous, muscle relaxant, volatile agent usually isoflurane 0.5-1 MAC

•  TIVA (propofol, NMB, narcs, dex) •  Hyperventilate to PaCO2 of 25-30 •  No PEEP unless needed •  IVF= 0.9% NaCl; avoid dextrose containing and hypoosmolar

solutions •  Can use hetastarch and albumin; remember fluid shifts are

minimal •  Goals wrt to fluids in neuro: keep them dry but maintain CePP

Anesthesia and craniotomy for mass lesions Emergence

•  Emergence is as important as induction •  Extubation is important to allow for neurological

examination of patient •  Sloppy emergence may result in sloppy outcome •  Sloppy emergence---> Cerebral edema and

hemorrhage among other things •  Extubate patients if normal criteria are met + if

High ICP is not out of control •  Reverse NMB, control BP carefully with drugs

and wake patient up once head clamp is off

Anesthesia for Posterior Fossa Craniotomy Introduction

•  3 main problems exist here •  Unusual Positioning •  Potential for brainstem injury •  Obstructive hydrocephalus

Anesthesia for Posterior Fossa Craniotomy Obstructive Hydrocephalus

•  Small lesions can have a significant effect on ICP as obstruction to CSF outflow can occur at the level of 4th ventricle and cerebral aqueduct

•  Patient will probably get ventriculostomy prior to induction of anesthesia

Anesthesia for Posterior Fossa Craniotomy Brainstem Injury

• Vital respiratory and circulatory centers can be injured by tumor, aneurysms and surgery itself • Injury take the form of ischemia or infarction • Clinical sequel include: postop apnea, aspiration, hypotension and bradycardia (and other rhythm disturbances)

Anesthesia for Posterior Fossa Craniotomy Positioning

•  Most cases done in prone or lateral positions •  Rarely done in sitting positions (on exams) •  Most of the time, the head is above the heart

regardless of position •  Head clamp and associated problems still present •  Advantage of sitting position: Less blood loss and

better exposure •  Avoid injuries to peripheral nerves, ischial spine

and head and eyes when positioning

Anesthesia for Posterior Fossa Craniotomy Premedication

•  Same as for supine tumors

Anesthesia for Posterior Fossa Craniotomy Maintenance

•  Same as supine crani’s •  Can avoid nitrous if sitting position or if the

patient has pneumocephalus •  As always, turn off nitrous once dura is close in

any crani case •  Use of nitrous oxide is very controversial in

anesthesia

Anesthesia for Posterior Fossa Craniotomy Problems

•  Positioning: covered already •  Pneumocephalus: just mentioned •  Postural hypotension •  Venous air embolism

Anesthesia for Posterior Fossa Craniotomy Problems: Postural Hypotension

•  Why does this happen: •  Fluid restriction and diuresis •  Position itself •  Lower sympathetic tone with venous pooling in

the presence of volatile agents •  Treat with vasopressors carefully rather than large

amounts of fluid; perhaps lighten anesthesia too, compression stocking on

Anesthesia for Posterior Fossa Craniotomy Problems:Venous Air embolism

•  Occurs when pressure within a vein is sub-atmospheric •  Incidence is about 40% •  Contributory factors: low CVP, poor surgical techniques •  Physiological consequences: F(rate and amount of air);

small bubbles are well tolerated and are exhaled; if the lungs is overwhelmed then PAP increases, cardiac output decreases as RV after load increases

•  PaCO2 slight increase, PaO2 decrease if amount small •  Full hemodynamic compromise if large amounts of air •  Paradoxical Air Embolus: Can lead to CVA or coronary

artery occlusion. PAE occurs when RAP exceeds LAP in the presence of a patent foramen ovale

Anesthesia for Posterior Fossa Craniotomy Problems:VAE; Monitoring

•  TEE •  Precordial Doppler •  ETN2, ETCO2, Etvolatile agent •  Changes in PAP and CVP •  Changes in ECG and Blood Pressure (very

late)

Anesthesia for Posterior Fossa Craniotomy Problems:VAE; Placement of CVP

•  Place multiorificed CVP at the junction of RA and SVC

•  Easiest done with Fluoroscopy •  Also done with ECG looking for a biphasic p

wave and then pulling back

Anesthesia for Posterior Fossa Craniotomy Problems:VAE: Treatment

•  Surgeon flood area •  100% O2 and turn off nitrous •  Aspirate CVP •  Fluids •  Vasopressors to correct hypotentsion •  Bilateral jugular compression •  PEEP (?); this may cause paradoxical embolism •  If all else fails: turn the patient to LLD position •  Finally start CPR in the supine position and prepare for Wednesday

morning

Anesthesia for Aneurysms and AVMs Preoperative Management

•  Same goals as patients with tumors •  Most patients have normal ICP unless the

aneurysm is ruptured

Anesthesia for Aneurysms and AVMs Intraop Management

•  Anesthetic technique very similar to tumors •  Goals: Prevent rupture, ischemia and avoid/exacerbate vasospasm

•  Few exceptions exist: •  ICP may be normal so hyperventilation usually avoided unless it

helps expose the aneurysm •  Induced hypotension may be employed •  Barbiturate coma may be needed •  Potential for huge blood loss present •  Hyperventilation also avoided in patients with vasospasm

•  In cases of rupture: Get help fast; lower blood pressure if needed,100% oxygen, prepare for barbiturate coma

Anesthesia for Aneurysms and AVMs Intraop Management

•  Make sure you have large bore IV access •  Can justify central line placement for access and

intravascular volume measurement •  Cordis placement good idea especially in cases of

large AVMs

Anesthesia for Aneurysms and AVMs Extubation

•  If extubation is planned, you need to have complete control of blood pressure. Have a plan ready and be ready to act fast.

•  In case of large AVM’s, some advocate postop intubation because of risk of bleeding postop.

GDC

•  Minimal invasive aneurysm surgery

•  Anesthesia set up •  Our track record •  Problems: Bleeding

(rupture) and ventriculostomy problems

•  Goals: Like aneurysm

Carotid Endarterectomy Preop Evaluation

•  Most common surgery for patients with TIAs or carotid stenosis of >70%

•  Normal H&P,labs as in all patients •  Attention paid to cardiovascular (HTN,

CAD) and neurological disease (TIA, syncope, CVA)

•  These patients are “true vasculopaths” •  Allows interpretation of postop deficits

from existing ones

Carotid Endarterectomy Anesthesia Management

•  Goals of Anesthesia •  Maintain CePP and CeBF •  Critical part of case is during cross clamping of

diseased artery; one is dependant on collateral flow •  Some surgeons place shunts to decrease dependence on

collateral circulation •  Some place shunts when monitoring indicates need for

one •  Stump Pressure another way to “measure collateral

flow”

Carotid Endarterectomy Anesthesia Management: Monitors

•  ASA monitors •  A-line: Positioning, rapid changes in BP, access

for electrolytes and PaO2 and PaCO2 •  Central Access: Not unless otherwise indicated •  Foley Monitor: usually no •  NMB Monitor: yes if GA •  Neurologic Monitors as needed: EPs, EEGs if GA

Carotid Endarterectomy Anesthesia Management: Local Anesthesia

•  Choice include local by surgeons and MAC by anesthesia •  Choice of superficial and deep cervical plexus block •  Advantage:

•  Monitor patients motor function •  NOT ENTIRELY RELIABLE; CVAs can occur despite normal

function intraop •  Disadvantage

•  Slow surgeons taking too long •  Patient position, cooperation, coughing, claustrophobia

•  No diff: Blood pressure management, risk of CVA, cerebral protection, better monitoring, risk of postop cardiovascular complications

Carotid Endarterectomy Anesthesia Management:General Anesthesia

•  Induction: Thiopental, Etomidate,propofol •  Maintenance: N20, isoflurane or other volatile anesthetic, narcotics and

NMB •  Some administer thiopental 3-5 mg/kg immediately before clamping

the carotid; no data to suggest barbiturates reduce morbidity after CEA •  Goal: maintain CePP: maintain blood pressure close to patients

normal range if available •  Maintain BP: fluids and phenylephrine drip (10-80 mcg/min) •  Avoid HTN: Leads to cerebral edema especially in areas of ischemia

that have lost auto regulation; also leads to increase myocardial work by increasing afterload

Carotid Endarterectomy Anesthesia Management

•  Ventilation: maintain PaCO2 around 35. Do not hyperventilate (ischemia)

Carotid Endarterectomy Anesthesia Management: Postop Problems

•  Common Problems: •  BP lability: Hypotension and HTN in previously HTN patients

•  HTN: Treat with NTG and NTP •  HTN: Mechanism:NK; perhaps secondary to denervation or altered

sensitivity of carotid sinus •  Hypotension: Also altered sensitivity of carotid sinus (shielded by

plaque before) •  Tracheal compression due to hematoma formation •  Loss of carotid body function •  Myocardial Infarction •  CVA (most are embolic)

Brain Biopsy

•  Function: Obtain brain tissue to determine course of action

•  Anesthetic technique: MAC acceptable if patient is psychologically competent; GA otherwise

•  Remote location: Have everything available

Trigeminal Decompression

•  Function: To alleviate pain secondary to TG nerve compression

•  Anesthetic: General Anesthesia as the procedure is very painful; Use of atropine or glycopyrolate to avoid vagal response.

•  Also a remote location